1. Field of the Invention
The present invention relates to a surgical device and method for creating a channel in a region of tissue and simultaneously or promptly thereafter, delivering a therapeutic agent in, near or around the channel and more particularly to a device and method for performing a transmyocardial revascularization procedure in combination with delivery of a therapeutic substance in and around the treated region of the myocardium of the heart.
2. Description of the Prior Art
Living tissue becomes ischemic when starved of oxygen and nutrients, usually because the tissue is not receiving adequate blood supply. Ischemia can be caused by a blockage or narrowing in the vascular system that prohibits an adequate supply of oxygenated blood from reaching the affected tissue area. Ischemia can lead to pain in the area of the affected tissue and, in the case of certain muscle tissue, can interrupt muscular function. Ischemia is reversible, such that cells may return to normal function once they receive the proper blood flow. It is believed ischemic tissue can remain in a hibernating state, preserving its viability for some time despite the deprivation of oxygenated blood. Restoring blood flow to the ischemic region is the only known method to accomplish revival of the ischemic tissue. Although ischemia can occur in various regions of the body, ischemia of the myocardium of the heart is well known due to coronary artery disease or occlusion of the coronary arteries, which otherwise provide blood to the myocardium.
Atherosclerosis or narrowing of the artery is a leading cause for inadequate blood flow to the heart. In addition to the narrowing, atherosclerosis can result in loose plaque dislodging within an artery. This loose plaque can travel through the arterial system until it becomes lodged within a narrower portion of the arterial system. The resulting blockage can lead to an acute infarcted area of the myocardium.
Ischemia and myocardial infarct are two important cardiac disease states. Symptoms are those included in the constellation of symptoms referred to as angina pectoris, and include constricting pain in the chest and radiating pain in the arms, neck and jaw. Ischemia of the tissue of the heart is characterized by limited metabolic processes which causes poor functionality, and may lead to fibrillation and death. Thus, the normal contractile functioning of the myocardial heart cells is hindered in an ischemic region. If an ischemic, or damaged, region of the heart does not receive enough blood flow and nutrients to sustain the myocardial cells, even when in a hibernating state, they are said to die and become infarcted. Infarcted myocardial tissue may also lead to fibrillation and death.
Treatment of myocardial ischemia has been addressed by several techniques designed to restore blood supply to the affected region. One procedure, coronary artery bypass grafting (CABG), involves grafting a venous segment between the aorta and the coronary artery to bypass the occluded portion of the artery. Once blood flow is redirected to the portion of the coronary artery beyond the occlusion, the supply of oxygenated blood is restored to the area of ischemic tissue.
Ischemic myocardium tissue resulting from atherosclerosis can also be treated through stenting the diseased area of the artery. In this procedure, a catheter is passed into the vascular occlusion. A stent is placed at the occlusion site and expanded within the artery to increase the vascular opening and increase blood flow. Alternatively, an angioplasty procedure can be performed to open the narrow vascular passageway. In this procedure, a balloon catheter is passed into the occluded site and the balloon inflated to increase the vascular opening. While effective to increase blood flow for a period of time, these procedures have numerous disadvantages and limitations, including an inability to prevent continued atherosclerosis.
Another method for treating ischemic myocardium is called transmyocardial revascularization (“TMR”), the creation of pathways or channels in the myocardium of the heart. The procedure using needles in a form of surgical “myocardial acupuncture” has been used clinically since the 1960s. In this method, small channels are created either completely through the myocardium in an open surgical procedure or partially through the myocardium from the endocardial layer in a percutaneous procedure. Various modalities may be used to create these channels, including mechanical means, laser energy, radiofrequency energy, ultrasonic energy, resistive heating, and cryoablation. These channels may create an area of injury that is believed to spur the natural healing process. A desirable part of this healing process is the creation of new blood vessels that may help to alleviate the ischemic condition within the myocardium.
Yet another method to treat ischemic tissue, and particularly ischemic myocardial tissue, is through therapeutic agent therapy. Therapeutic agent therapies with angiogenic and myogenic growth factors may expedite and/or augment collateral artery development. In the field of therapeutic agent delivery, many techniques currently exist for delivering therapeutic agents or other materials including, but not limited to, biologics to the human body. These include, among others, oral administration, injection directly into body tissue such as through an intramuscular injection, transcutaneous injection in which a compound is injected directly into the vasculature of a patient, or topical administration. Although many situations are satisfactorily treated by the general or directed, typically systemic acting administration of a therapeutic agent, the treatment of ischemic tissue could be facilitated and/or improved by the ability to deliver or administer a biologic agent directly to or adjacent such tissue with control over such delivery. Recently, medicine has focused attention on treating diseases with conventional physical surgical procedures in combination with a local delivery of a drug or other therapeutic agent. For example U.S. Pat. No. 6,224,584, issued on May 1, 2001 to March, et al., which is hereby incorporated by reference in its entirety into this application, discloses a system for treating a patients heart by first forming channels in the heart and then delivering drugs or other therapeutic agents into those channels.
There are a number of important problems that are not addressed by the systems and methods of the present art. For example, none of the prior art teaches how to ablate a channel into a desired tissue and either simultaneously, or in various sequences, administer a therapeutic agent or any combination of agents into both the channel and into the tissue surrounding the channel. Moreover, the prior art does not teach a device and method for precise and effective ablation along with simultaneous controlled delivery of the desired agent or agents into the channel and surrounding tissue. None of the prior art systems discloses a device that allows for a surgeon to perform a combination TMR and direct delivery of a therapeutic agent using a single simple device and in the same procedure.